The dilated heart failure protocol entered 5 patients over the past year. All received right ventricular septal pacing, as this was found to be the site associated with the least decrement in cardiac function. One patient died after several months of pacing (the pacer was in fact not pacing at the time) the consequence of a ventricular fibrillation arrest. There was no evidence of pacemaker failure or any contribution of the pacemaker to this event. Another patient suffered a small right ventricular pericardial effusion after pacemaker implantation, likely due to perforation of the right heart by the pacer lead. He remains stable, although he recently developed a pericardial effusion that requried drainage and treatment for post-pericardiotomy-like syndrome. These complications may be expected in heart failure patients receiving a pacemaker, although they are rare. The other patients are alive and remain in the protocol. Most importantly, our acute pacing studies employing pressure-volume relation analysis in this patient group revealed that left ventricular pacing is likely to provide much greater benefit. We have developed methods of advancing a novel pacing lead into the coronary sinus and down to the vein draining the territory of the anterior descending artery. With this pacer wire, we can temporarily pace the left ventricular epicardium at the apex, or by withdrawing the catheter back to the base of the heart, pace near the mid LV or basal LV. Our work thus far has shown that these pacing sites are consistently associated with enhanced contractility, whereas this is very rare from traditional RV apical pacing locations, as well as from the RV septal site. We have also clarified that in only rare circumstances, placement of the RV pacing lead in the standard location is associated with a worsening of left ventricular function in patients with heart failure. As a result of these new acute data, and in combination with somewhat similar data from an ongoing European study, we have submitted an amendment to the JCCI and FDA that will incorporate LV pacing using minimal surgery (keyhole type operation) to place epicardial leads on the LV surface. Not all patients may require this, but in those in which the acute pacing study reveals clear advantages of LV pacing, this would then be possible to pursue chronically. We are awaiting word from the JCCI and FDA about this amendment, but are very enthusiastic. Some of the acute results from LV pacing alone have been truly remarkable and dramatic with respect to increases in LV cardiac output and systolic performance. Current plans are for recruitment of an additional 15 patients over the next year and a half.